import numpy as np
import pandas as pd

arr = np.arange(1, 10).reshape(3, 3)
df1 = pd.DataFrame(arr, columns=['a', 'b', 'c'])
df1.insert(0, 'key', ['001', '003', '002'])
print('第一个对象原始数据df1: \n', df1)
arr2 = np.arange(10, 14).reshape(2, 2)
df2 = pd.DataFrame(arr2, columns=['a', 'e'])
df2.insert(0, 'key', ['001', '004'])
print('第二个对象原始数据df2: \n', df2)
df3 = pd.concat([df1, df2])
print('纵向外合并的数据df3: \n', df3)
df4 = pd.concat([df1, df2], keys=['df1', 'df2'], sort=True)
print('纵向外合并，标记每个对象，并按列标签排序的数据df4: \n', df4)
df5 = pd.concat([df1, df2], join='inner', ignore_index=True)
print('纵向内合并并重新设置连续行标签的数据df5:\n', df5)
